This research will examine the importance of biological and physical causes of variation in the production of bioactive secondary metabolities by tropical seaweeds (including benthic, filamentous cyanobacteria) and invertebrates. The research has important biomedical consequences because it will specifically search for marine natural products with solid tumor selectivity (through NCI-sponsored research in collaboration with Dr. Fred Valeriote at Wayne State University Medical School), and it will focus on understanding what factors affect the yields of biomedically important marine natural products. First, differences in types and concentrations of secondary metabolites at different ages and life history stages, and among populations of selected seaweeds and invertegrateswill be examined. Facultative changes in chemical defenses will be examined for seaweeds, sponges, and soft corals exposed to: 1) increased grazing by fishes and specialist predators; and 2) different resources levels of light and nutrients. The proposed research will provide information on chemical variation and its causes and the ability and timing of seaweeds and invertebrates to change their allocation of chemical defenses. The study will contribute to our limited knowledge of the chemical variability of seaweeds and marine invertebrates, the biological properties of marine natural products, and the relationship between natureal adaptive functions of secondary metaolites and their biomedical potential. All extracts and isolated metabolies will be incorporated into established testing programs (UC Santa Barbara, Wayne State University Medical School) to determine their pharmacological activities in assays examining anti-inflammatory activity and solid tumor selectivity. Funding is requested primarily for personnel and supplies to carry out this Associate Investigator research. This program will provide research training opportunities for minority undergraduate and graduate (M.S. degree) students at the University of Guam, a predominantly undergraduate and minority institution.